Lebanon's Hizbullah Secretary-General Hassan Nasrallah described Tuesday's border clash between the Lebanese army and Israeli troops as "heroic" and warned his fighters would retaliate if there were further incidents. At least three Lebanese soldiers, one reporter and an Israeli officer were killed in the exchange of fire.

"The army fought heroic confrontation with the Israeli enemy in southern Lebanon," Nasrallah said in a speech marking the fourth anniversary of the 2006 war with Israel. He added that his movement's fighters were on standby to back the army. "This time we stood and watched ... but next we will not," he warned.

"Israel's aggression on Lebanon has never stopped. We will not stand idle ... we will cut any hand that attacks our army," Nasrallah said.

He also accused Israel of the 2005 assassination of ex-premier Rafiq Hariri and said he would unveil proof to that effect at a news conference next week. "I accuse the Israeli enemy of the assassination of (former) Prime Minister Rafiq Hariri and... I will prove this by unveiling sensitive information at a press conference on Monday," Nasrallah said.